1. Technical Field
The present disclosure relates generally to medical devices and methods and more particularly to catheter-based systems and methods useable for accessing, diagnosing, or treating defects in blood vessels, such as blood vessels of the brain.
2. Background of the Related Art
Stroke is a common cause of death and disability. In the United States, approximately 700,000 patients suffer from stroke annually. Stroke is a syndrome characterized by the acute onset of a neurological deficit that persists for at least 24 hours, reflecting focal involvement of the central nervous system, and is the result of a disturbance of the cerebral circulation. Its incidence increases with age. Risk factors for stroke include systolic or diastolic hypertension, hypercholesterolemia, cigarette smoking, heavy alcohol consumption, and oral contraceptive use.
Hemorrhagic stroke accounts for 20% of the annual stroke population. Hemorrhagic stroke often occurs due to rupture of an aneurysm or arteriovenous malformation (AVM), causing bleeding into the brain tissue and resultant infarction of brain tissue. The remaining 80% of strokes are due to ischemia that occurs due to occlusion of a blood vessel that deprives brain tissue of oxygen-carrying blood. Ischemic strokes are often caused by emboli or pieces of thrombotic tissue that have dislodged and traveled from other body sites, or from the cerebral vessels themselves, to occlude in the narrow cerebral arteries more distally. When a patient presents with neurological symptoms and signs, which resolve completely within 1 hour, the term transient ischemic attack (TIA) is used. Etiologically, TIA, and ischemic stroke share the same pathophysiologic mechanisms and thus represent a continuum based on persistence of symptoms and extent of ischemic insult.
Emboli occasionally form around the valves of the heart or in the left atrial appendage during periods of irregular heart rhythm and then are dislodged and follow the blood flow into the distal regions of the body. Those emboli can pass to the brain and cause an embolic stroke. As will be discussed below, many such occlusions occur in the middle cerebral artery (MCA), although such is not the only site where emboli come to rest.
When a patient presents with neurological deficit, a diagnostic hypothesis for the cause of stroke can be generated based on the patient's history, a review of stroke risk factors, and a neurologic examination. If an ischemic event is suspected, a clinician can tentatively assess whether the patient has a cardiogenic source of emboli, large artery extracranial or intracranial disease, small artery intraparenchymal disease, or a hematologic or other systemic disorder. A head CT scan is often performed to determine whether the patient has suffered an ischemic or hemorrhagic insult. Blood would be present on the CT scan in subarachnoid hemorrhage, intraparenchymal hematoma, or intraventricular hemorrhage.
To reach these lesions or occlusions microcatheter and microguidewire must be employed, but often the column support of these microcatheters is not strong enough to navigate through the distal reaches of the neurovasculature to effectively treat these sites. Often guide catheters are employed to act as a conduit to help support microcatheter access. Traditional guide catheters designed for coronary or peripheral use (U.S. Pat. Nos. 5,180,376 & 5,484,425 Fischell, U.S. Pat. No. 5,045,072 Castillo, U.S. Pat. No. 5,279,596 Castaneda, U.S. Pat. No. 5,454,795 Samson and U.S. Pat. No. 5,733,400 Gold), typically are not positioned above the skull base and limit their effectiveness in supporting microcatheters in the distal cerebrovasculature. Newer distal access guide catheters have been developed which are slightly longer, thinner, a bit more flexible than the early generations, but are constructed with the same manufacturing techniques as described in U.S. Pat. Nos. 5,180,376 & 5,484,425 Fischell, U.S. Pat. No. 5,045,072 Castillo, U.S. Pat. No. 5,279,596 Castaneda, U.S. Pat. No. 5,454,795 Samson and U.S. Pat. No. 5,733,400 Gold, but have not solved the kinking problem (e.g., Neuron Penumbra Recall—Oct. 2, 2009).